Factors That Influence Melting and Glass Transition Temperatures

14 FACTORS THAT INFLUENCE MELTING AND GLASS TRANSITION TEMPERATURES Melting Temperature 

During melting of a polymer there is a rearrangement of the molecnles in the transformation from ordered to disordered molecnlar states. Molecnlar chemistry and structure influence the ability of the polymer chain molecules to make these rearrangements and, therefore, also affect the melting temperatnre. 

Degree of branching also affects the melting temperatme of a polymer. The introduction of side branches introduces defects into the crystalline material and lowers the melting temperature. High-density polyethylene, being a predominately linear polymer. 

Bulky side groups from Table 15.2, the respective values for polypropylene and polystyrene are 18°C and lOO C. 

Polar groups for example, the values for poly(vinyl chloride) and polypropylene are 87°C and l C, respectively. 

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Factors that Influence Melting and Glass Transition Temperatures 603... 

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